Exemplary embodiments of the invention relate to a rotary wing aircraft, and more particularly, to a pivot bearing of an elastomeric bearing system configured for use in a rotary wing aircraft.
Flexbeam main rotor and tail rotor blade systems utilize resilient elastomeric bearings between a flexbeam and a surrounding torque tube. The elastomeric bearings position the torque tube relative to the flexbeam to permit the blade to pitch, flap, lead, and lag.
The elastomeric bearings are typically referred to as snubbers/dampers which include vertically stack arrangements of spherical and flat elastomeric laminates. The spherical bearing “snubber” accommodates pitch change and flapping rotation while the flat layers accommodate lead/lag linear motions and some radial span-wise motion. The snubber/dampers are located between the flexbeam and the torque tube under a preload so that the elastomer laminates thereof remain in compression throughout the full range of articulation. The snubber/dampers are often mounted through an opening in the torque tube for attachment to a retainer plate which is bonded to the flexbeam.
Conventional elastomeric bearing may fail in response to a retainer plate disbond. After a retainer disbond, the elastomeric bearings are pulled outboard and into contact with an adjacent motion limiter due to a combination of centrifugal force and bearing preload along the sloped flexbeam. Line contact is typically formed between the elastomeric bearing and the adjacent motion limiter when the elastomeric bearing is disbonded from the retainer. The outboard displacement is such that contact between the elastomeric bearing and the motion limiter may result in damage to the elastomeric bearing, the flexbeam, and the torque tube. As a result, the elastomeric bearing, motion limiter, and flexbeam is typically inspected every 50 hours of operation.